This invention relates generally to the field of clamping devices for aligning and holding the ends of pipes during the welding of the pipe ends. In particular, this invention relates to a pipe clamp which mounts on the inside diameter of two pipe ends and which provides a means for supporting the pipe ends while they are being welded together and for inspecting the inside diameter surface of the weld without removal of the pipe clamp or releasing of the purge gas seal.
When welding together sections of pipe, such as when fabricating a pipeline, it is known in the art to utilize a clamping device to align the ends of the pipes and to hold the pipe ends steady during the welding process. The pipe welds are typically inspected from the pipe exterior after the weld is completed. A volumetric inspection from the pipe exterior will reveal any defect throughout the weld's thickness. When a defect is found, a repair is made by machining or grinding the weld metal until the defect is removed, then rewelding the repair area. Defects may originate in the root pass of the weld as a result of misalignment of the pipe ends, contamination of the weld metal, improper welding process parameters, etc. Defects in the root pass may require removal of the entire thickness of the weld. Therefore, it is desirable to inspect the root pass prior to continuing the welding process to identify defects before they are covered by further layers of weld metal. The outside surface of the root pass is usually accessible to the weld operator or inspector, however, some defects may not be detectable without access to the inside diameter of the pipe, especially if a visual inspection technique is being used. With prior art pipe clamps, such as the device taught in U.S. Pat. No. 5,090,608, the pipe clamp must be removed in order to gain access to the I.D. of the root pass. With this type of prior art clamp, any inert gas purge seal established inside the pipe around the weld joint area would have to be broken for the inspection to take place, then reestablished if a repair weld was needed. Removal of the pipe clamp after completion of only the root weld pass may also result in unacceptably high stresses on the weld metal due to forces in the pipes.